Sunday, July 25, 2010

Redwoods Aren't That Ancient or Special

Redwood Preserve in the Oakland Hills.

It's a common claim on informational signs in California parks that "redwoods were around at the time of the dinosaurs", or some such statement. While they're certainly amazing organisms, are these really tree-coelacanths?

Timetree consistently gives a divergence of trees in the order Cupressaceae (redwoods, junipers, various cypresses) at 80 MYA. We know from well-preserved fossilized trees that there were trees growing in the late Cretaceous that looked like modern redwoods, in the same place that modern redwoods grow. (This particular petrified forest near Napa, California is by far the most amazing petrified forest I've ever seen. I had to touch the trees to convince myself they're stone and not wood.)

Because fossilized "redwoods" date back to just after the putative divergence time, it's likely that modern redwoods are merely the more-ancestral-appearing descendants (relative to junipers and cypresses) of the these ancestral trees. Although the size and bark of the fossilized trees look similar to the redwoods today, that certainly doesn't tell the whole story about them, although barring miraculously preserved 65-million-year old Cretaceous tree DNA, that's about all we'll get. Consequently those old trees would more appropriately be called ancestral cypresses. Maybe the Ancient Giant Cypress?

Either way, redwoods are still pretty special, although not in the way that their chromosomes somehow resisted entropy for 65 million years.

Words to Live By

"...there is good and bad speculation, and this is not an unparalleled activity in science...Those scientists who have no taste for this sort of speculative enterprise will just have to stay in the trenches and do without it, while the rest of us risk embarrassing mistakes and have a lot of fun." - Dan Dennett